The effects of the interface traps on the quantum efficiency and the crosstalk of a back-illuminated p-on-n mesa InSb photovoltaic infrared detector were studied based on Silvaco 2D numerical simulation. The distributions of the recombination rate, the hole current density and the electric field change with the position and the density of the interface traps, and their relationships were analyzed. The results show that the interface traps has a profound effect on the inherent physical mechanisms of the steady-state performance of the InSb detector. The traps at the N-InSb/passivation interface both on the back and between the pixel mesas improve the crosstalk performance at the cost of the decrease in the quantum efficiency. Because the regions they affect are different, the influence extents of the traps at different positions on the two steady-state performance are different.